Syringe with self-returnable plunger

ABSTRACT

A plunger-type syringe is provided in which the plunger returns after it is depressed. The syringe includes an elastic membrane which is received by the tubular barrel and interposed between the barrel and the plunger. The open rear end of the barrel is provided with a plurality of circumferentially spaced rearwardly extending pointed projections, and a portion of the membrane extends over the projections and is secured against longitudinal movement thereby. Another portion of the membrane is engaged by the plunger for longitudinal movement with the plunger within the barrel, and as the plunger is depressed, the membrane is stretched and provides a force tending to return the plunger to its original position. When the plunger is released, the elastic membrane returns the plunger.

United States Patent 1 Beich 1 SYRINGE WITH SELF-RETURNABLE PLUNGER [75] Inventor: Frank R. Beich, Wilmette, Ill.

[73] Assignee: American Hospital Supply Corporation, Evanston, Ill.

[22] Filed: June 3, 1971 [21] Appl. No.: 149,486

Related US. Application Data [63] Continuation-impart of Ser. No. 35,846, May 8, 1970,

Pat. No. 3,661,152.

[52] US. Cl. 222/341, 128/218 PA, 128/234,

222/386.5 [51] Int. Cl A6lm 5/00 [58] Field of Search 222/3865, 341, 371;

128/218 PA, 218 F, 234, 235

[56] References Cited UNITED STATES PATENTS 1,414,135 4/1922 Ingram 222/341 June 12, 1973 Primary Examiner-Samuel F. Coleman Assistant ExaminerThomas E. Kocovsky Att0rneyDawson, Tilton, Fallon & Lungmus [57] ABSTRACT A plunger-type syringe is provided in which the plunger returnsafter. it is depressed. The syringe includes an elastic membrane which is received by the tubular barrel and interposed between the barrel and the plunger. The open rear end of the barrel is provided with a plurality of circumferentially spaced rearwardly extending pointed projections, and a portion of the membrane extends over the projections and is secured against longitudinal movement thereby. Another portion of the membrane is engaged by the plunger for longitudinal movement with the plunger within the barrel, and as the plunger is depressed, the membrane is stretched and provides a force tending to return the plunger to its original position. When the plunger is released, the elastic membrane returns the plunger.

8 Claims, 12 Drawing Figures SYRINGE WITH SELF-RETURNABLE PLUNGER RELATED APPLICATION This application is a continuation-in-part of the prior application entitled .Syringe with Self-Returnable Plunger, Ser. N0. 35,846, filed May 8, 1970 now US. Pat. No. 3,661,152.

BACKGROUND OF THE INVENTION This invention relates to syringes, and, more particularly, to piston-type syringes suitable for medical use.

The invention finds particular utilityin medical irrigation syringes but is not limited to that particular type of syringe. Irrigation syringes, which may be used in irrigating incisions, wounds, body passages, wet dressings or the like, are generally of two types the piston-type or the bulb-type. A piston syringe includes a barrel and a piston or plunger which is slidable longitudinally within the barrel to eject fluid from the barrel or to draw fluid into the barrel. A bulb syringe includes a barrel and an elastic bulb which is squeezed to eject fluid from the barrel and released to draw fluid into the barrel. A variation of the bulb syringe is the bellows syringe in which a bellows is collapsed to eject fluid and allowed to expand to draw fluid into the barrel.

Each of these syringes has advantages and disadvantages. For example, a piston syringe can exert a relatively large force, particularly during suction when the plunger can be manually pulled away from the nozzle or ejector end of the syringe to draw fluid into the barrel. However, a problem with this type of syringe is that too much force may be delivered or provided. Further, the operator must use both hands to return the plunger one hand to grasp the barrel and the other to pull the plunger.

A bulb syringe provides a more gentle suction action, but if the nozzle of such a syringe becomes clogged during suction, expansion of the bulb will be prevented and a positive return force cannot be applied by the operator as in the case of a piston syringe.

SUMMARY The inventive syringe combines the advantages of both the piston syringe and the bulb syringe without the attendant disadvantages. The syringe includes a plunger which provides a smooth, continuous ejecting action. As the plunger is depressed, the elastic membrane is stretched and creates a force which acts protectively to restrain delivery of fluid at too rapid a rate. When the pressure on the plunger is released, the elastic membrane provides a relatively mild suction force to return the plunger to its original position while the syringe is held by only one hand. Even though the membrane is tensioned considerably as the plunger is depressed, the rear portion of the membrance is se curely anchored against longitudinal movement with the plunger by means of the circumferentially spaced rearwardly extending pointed projections on the barrel. The annular rear wall of the membrane passes over these projections, and the projections dig into the rear wall as the membrane is tensioned. The projections are molded integrally with the plunger and are provided with sharp points without the necessity of any finishing operations. Accordingly, the syringe can be produced inexpensively enough to allow it to be discarded (and incinerated) after a single use, thereby avoiding the serious problems of cross contamination which have been found to arise when instruments are re-used, even after supposedly effective sterilizing procedures.

DESCRIPTION OF THE DRAWING The invention will be explained in conjunction with an illustrative embodiment shown in the accompanying drawing, in which;

FIG. 1 is a perspective view of a syringe formed in accordance with the invention;

FIG. 2 is an exploded view of the barrel of the syringe and the membrane;

FIG. 3 is an elevational view, partially broken away, of the syringe with the plunger being depressed;

FIG. 4 is a fragmentary view similar to FIG. 3 showing the plunger in its non-depressed position;

FIG. 5 is an elevational view partially broken away of the membrane in an untensioned position;

FIG. 6 is a sectional view taken along line 66 of FIG. 5;

FIG. 7 is a sectional view taken along line 77 of FIG. 5;

FIG. 8 is an enlarged fragmentary top plan view of the barrel;

FIG. 9 is a fragmentary view taken along line 9--9 of FIG. 8;

FIG. 10 is a sectional view taken along line 10-l0 of FIG. 9;

FIG. 11 is a fragmentary sectional view taken along the line 11-11 of FIG. 10; and

FIG. 12 is a fragmentary view taken along line l2-12 of FIG. 8.

DESCRIPTION OF SPECIFIC EMBODIMENT Referring now to the drawing, the numeral 15 designates generally a syringe formed in accordance with the invention which includes an elongated generally tubular barrel 16, a plunger or piston 17, and an elastic membrane 18 interposed therebetween. The particular syringe 15 illustrated is a medical irrigation syringe, but it is to be understood that the invention may be used with other types of syringes.

The barrel 16 includes a generally cylindrical body portion 19 which merges with a generally .frustoconical nozzle portion 20 provided with an open forward end 21 through which fluids may pass. The barrel is provided with an open rear end 22, and the rear portion of the cylindrical wall of the barrel terminates in a plurality of pointed projections 23, which will be explained in detail hereinafter. A radially outwardly extending annular flange 24 is spaced longitudinally forwardly from the projections, and a pair of finger grips 25 extend radially outwardly from the flange at generally diametrically opposed positions.

The plunger 17 extends through the open rear end of the barrel and is slidably received therein. The forward end of the plunger terminates in a generally cylindrical disc or plug portion 27 (FIG. 3), and the other end terminates in a radially enlarged disc portion 28 adapted to be pressed by the thumb of the operator. The particular plunger illustrated includes a central portion 29 formed of four intersecting planar portions or ribs 30 which provides an economical and light yet extremely sturdy plunger. An angular groove 31 is provided in the forward disc portion 27 for cooperation with the membrane as will be explained more fully hereinafter.

The elastic membrane or diaphragm 18 includes a barrel attaching portion 33 and a. plunger portion 34 joined by three axially extending connecting bands 35. Referring particularly to FIGS. 3 and 5, the plunger portion 34 of the membrane includes a generally cylindrical wall portion 36, a frusto-conical nose 37, and an elongated, somewhat bullet-shaped projection 38 which is sized to be received by the nozzle portion of the barrel and which serves to force a greater amount of fluid from the barrel. A pair of axially spaced circumferentially extending sealing ribs or flanges 39 and 40 extend radially outwardly from the cylindrical wall 36 and are sized to be compressed by the inner surface of the cylindrical body of the barrel to provide a fluid-type seal therewith. An annular attaching flange 41 extends inwardly from the wall 36 generally opposite the upper rib 39 and is received by the annular groove 31 of the plunger to secure the membrane to the plunger for longitudinal movement therewith in either direction.

The barrel-attaching portion 33 of the membrane includes an annular rear wall 42 which extends radially outwardly from the axially extending bands 35 and an axially extending cylindrical outer wall 43 which has an inside diameter slightly less than the outside diameter of the barrel. The elastic connecting bands 35 of the membrane extend between the plunger portion 34 and the inner edge of the annular rear wall 42 of the barrelattaching portion, and the particular embodiment illustrated includes three connecting bands spaced 120 apart. It is to be understood, however, that the number and location of the connecting bands can be varied, and the barrel-attaching portion and plunger portion may even be connected by continuous, generally cylindrical connecting portions.

Referring now to FIGS. 8-11, the projections 23 at the rear of the barrel are seen to be generally pyramidal and include a generally triangular arcuate surface 46 which extends longitudinally from the outer surface of the cylindrical barrel and which has the same curvature. This arcuate surface has a pair of inclined side edges 47 which form an included angle of about to about 60, and a pair of planar triangular surfaces 48 and 49 extend from these inclined edges 47 and intersect along line 50 which extends from the inner surface of the cylindrical barrel to the apex 51 of the arcuate outer surface 46. Each inclined side edge 47 of each arcuate surface intersects with an inclined side edge of an adjacent projection to provide the barrel with a continuous sawtooth-like rear end. The planar surfaces 48 and 49 terminate at a planar ledge 52 which extends radially inwardly from the intersections of the inclined side edges 47 of adjacent projections.

The shape of the sawteeth or projections enable the teeth and the remainder of the barrel to be molded integrally from plastic, and the three intersecting surfaces which form, the teeth provide a sharp apex without finishing operations. in one specific embodiment the included angle between the side edges 47 of each tooth was about 55, and each side edge extended at an angle of about 625 from the planar ledge 52. The included angle between inclined edges 47 of adjacent teeth was also about 55, and the wall of the barrel was about l/l6 inch thick.

Referring now to FIGS. 3 and 4, the barrel-attaching portion of the membrane is secured to the rear end of the barrel by sliding the outer wall 43 of the membrane forwardly over the rear end of the barrel. The rear wall 43 is sized to be received relatively snugly on the barrel, and the points of the teeth 23, which lie along the cylindrical outer surface of the barrel, engage the barrel-attaching portion of the membrane at the juncture between the rear wall 42 and the outer wall 43.

When the syringe is not being used, the plunger and the membrane assume the position shown in FIG. 4. The connecting bands 35 of the membrane are in a relaxed, unstretched state and extend for only a minor portion for the length of the barrel.

When the syringe is to be used, the operator grasps the barrel between two fingers of one hand and depresses the plunger by forcing the disk portion 28 downwardly with the thumb, the finger grips 25 permitting the barrel to be firmly held. As the plunger moves downwardly, the connecting bands 35 stretch and tension the rear wall 42 of the membrane. However, as the inner edge of the annular rear wall is pulled downwardly by the bands, the teeth 23 dig firmly into the membrane and prevent the barrel-attaching portion of the membrane from being pulled into the barrel.

The plunger may be depressed until the desired volume of fluid will be drawn into the barrel upon release of the plunger, and the constricted neck portion 16a joining the tubular body of the barrel to the nozzle 20 provides a positive stop to ensure that the connecting bands 35 are not excessively stretched. After the plunger has been depressed the desired distance, the pressure exerted by the thumb may be released, and the stretched elastic connecting bands smoothly return the plunger toward its original position while the syringe is held with one hand. The seal provided by the membrane will provide a gentle sucking action as the plunger returns, and fluid'may be drawn into the barrel through the open end of the nozzle.

The fluid may be ejected from the barrel when desired by again depressing the plunger, and the elastic connecting bands provide a force which acts protectively to aid in preventing the fluid from being ejected too fast.

Under ordinary conditions the syringe requires the use of only a single hand. However, if the nozzle be comes clogged while the fluid is being drawn into the barrel or if additional suction force is desired, the plunger can be manually retracted. The membrane is connected to the plunger by the inwardly extending flange 41, and a rearward pull on the plunger will also pull the membrane rearwardly.

Both the barrel and the plunger can advantageously and economically be formed of molded plastic, and the membrane can be molded from a suitable elastic material such as rubber, certain well known plastics, and the like. We have found that syringes formed in accordance with the invention can be produced more inexpensively than many of the syringes heretofore available, and our syringes therefore can be economically disposed of after a single use, thereby eliminating possible cross-contamination if the syringe is used more than once.

If it is desired to use the syringe a number of times, the various parts thereof can easily be separated for cleaning. The membrane can be separated from the barrel merely by withdrawing the barrel attaching portion rearwardly from the barrel as the plunger is withdrawn, and the plunger portion of the membrane can be removed from the plunger by flexing the attaching flange 41 away from the annular groove 31 in the plunger. Similarly, if the membrane becomes fatigued through excessive use, it can be easily be replaced with a new membrane.

While in the foregoing specification, a detailed de scription of a specific embodiment of the invention was set forth for the purpose of illustration, it is to be understood that many of the details herein given may be varied considerably by those skilled in the art without departing from the spirit and scope of the invention.

I claim:

1. A syringe comprising an integrally molded elongated tubular barrel having a generally cylindrical wall having an open rear end and terminating in a plurality of circumferential spaced rearwardly extending pointed projections, an elongated plunger slidably disposed in the barrel and projecting from the open rear end thereof, a stretchable elastic membrane extending between the barrel and the plunger, the membrane including a barreLattaching portion having an annular rear wall extending radially outwardly adjacent the pointed projections and a cylindrical outer wall extending forwardly from the annular rear wall along the outer surface of the wall of the barrel and a plungerattaching portion engaging the plunger for longitudinal movement therewith within the barrel, the points of the projections digging into the annular rear wall of the membrane as the plunger is moved forwardly within the barrel to anchor the barrel-attaching portion.

2. A syringe having an elongated tubular barrel with an open rear end and an orifice at the front end, a plunger slidably disposed in the barrel and projecting from the open rear end thereof, a stretchable elastic membrane extending between the barrel and the plunger, the membrance including a first portion engaging the barrel at the rear end thereof and being restrained against longitudinal movement thereby, a second portion engaged by the plunger for longitudinal movement therewith, the membrane being stretchable toward the front end of the barrel as the plunger is moved longitudinally toward the front end of the barrel, the rear end of the barrel terminating in a plurality of rearwardly extending relatively sharp projections engaging the first portion of the membrane to hold the first portion of the membrane as the membrane is stretched toward the front end of the barrel.

3. The syringe of claim 2 in which the tubular barrel includes a generally cylindrical wall and the projections extending longitudinally from the wall at circumferentially spaced locations therearound. V

4. The syringe of claim 2 in which the first portion of the membrane includes an annular rear wall extending radially outwardly adjacent the projections on the rear end of the barrel and an outer wall extending longitudinally from the annular rear wall along the outside of the barrel, the projections engaging the annular rear wall for anchoring the first portion of the membrane as the plunger and the second portion of the membrane move toward the orifice of the barrel.

5. The syringe of claim 2 in which the barrel is formed of molded plastic and includes a generally cylindrical wall and the projections are molded integrally with the wall and extending longitudinally from the wall at circumferentially spaced locations therearound.

6. The syringe of claim 5 in which each projection is generally pyramidal and includes an arcuate generally triangular surface extending longitudinally from the outer surface of the cylindrical wall of the barrel and having a pair of inclined side edges terminating in a pointed apex, and a pair of substantially planar generally triangular surfaces, each planar surface extending from one of the inclined side edges and intersecting the other plan surface along a line extending from the inner surface of the barrel to the apex.

7. The syringe of claim 6 in which each inclined side edge of each projection intersects an inclined side edge of the adjacent projection.

8. The syringe of claim 6 in which the included angle between the inclined side edges of each projection is about 45 to'about 60. 

1. A syringe comprising an integrally molded elongated tubular barrel having a generally cylindrical wall having an open rear end and terminating in a plurality of circumferential spaced rearwardly extending pointed projections, an elongated plunger slidably disposed in the barrel and projecting from the open rear end thereof, a stretchable elastic membrane extending between the barrel and the plunger, the membrane including a barrel-attaching portion having an annular rear wall extending radially outwardly adjacent the pointed projections and a cylindrical outer wall extending forwardly from the annular rear wall along the outer surface of the wall of the barrel and a plunger-attaching portion engaging the plunger for longitudinal movement therewith within the barrel, the points of the projections digging into the annular rear wall of the membrane as the plunger is moVed forwardly within the barrel to anchor the barrel-attaching portion.
 2. A syringe having an elongated tubular barrel with an open rear end and an orifice at the front end, a plunger slidably disposed in the barrel and projecting from the open rear end thereof, a stretchable elastic membrane extending between the barrel and the plunger, the membrance including a first portion engaging the barrel at the rear end thereof and being restrained against longitudinal movement thereby, a second portion engaged by the plunger for longitudinal movement therewith, the membrane being stretchable toward the front end of the barrel as the plunger is moved longitudinally toward the front end of the barrel, the rear end of the barrel terminating in a plurality of rearwardly extending relatively sharp projections engaging the first portion of the membrane to hold the first portion of the membrane as the membrane is stretched toward the front end of the barrel.
 3. The syringe of claim 2 in which the tubular barrel includes a generally cylindrical wall and the projections extending longitudinally from the wall at circumferentially spaced locations therearound.
 4. The syringe of claim 2 in which the first portion of the membrane includes an annular rear wall extending radially outwardly adjacent the projections on the rear end of the barrel and an outer wall extending longitudinally from the annular rear wall along the outside of the barrel, the projections engaging the annular rear wall for anchoring the first portion of the membrane as the plunger and the second portion of the membrane move toward the orifice of the barrel.
 5. The syringe of claim 2 in which the barrel is formed of molded plastic and includes a generally cylindrical wall and the projections are molded integrally with the wall and extending longitudinally from the wall at circumferentially spaced locations therearound.
 6. The syringe of claim 5 in which each projection is generally pyramidal and includes an arcuate generally triangular surface extending longitudinally from the outer surface of the cylindrical wall of the barrel and having a pair of inclined side edges terminating in a pointed apex, and a pair of substantially planar generally triangular surfaces, each planar surface extending from one of the inclined side edges and intersecting the other plan surface along a line extending from the inner surface of the barrel to the apex.
 7. The syringe of claim 6 in which each inclined side edge of each projection intersects an inclined side edge of the adjacent projection.
 8. The syringe of claim 6 in which the included angle between the inclined side edges of each projection is about 45* to about 60*. 